I tried joining a gym in 2019, I went every day for an hour and was making decent progress. Then covid happened, the gym closed, but they wouldn't let me cancel unless I went in person.

So I stopped putting money on the greendot card I used for the membership. I got a few phone calls from them, and ignored them after the first.

I imagine sooner or later they will get wise to this and demand a bank account number, which could be defeated by opening a "gym account" that only has enough for one month's membership.